1. Field of the Invention
The present invention relates to a vehicular lamp for an automobile, and more particularly to a vehicular lamp of a thin design for an automobile.
2. Related Art
In a vehicular lamp for an automobile which is used as a tail lamp or the like of an automobile, a reflector, having a required surface (particularly, a paraboloid) , is used in order to form light, emitted from a bulb (serving as a light source) into required light distribution characteristics. However, in this reflector, its dimension in a direction of an optical axis is larger than a dimension of an opening, and as a result a dimension of the vehicular lamp in a forward-rearward direction is increased, which constitutes a barrier to a thin design of the vehicular lamp.
Therefore, there has heretofore been proposed a structure in which a reflective surface of a reflector is divided into a plurality of regions, and these divided surfaces are offset in a direction of an optical axis, thereby achieving a thin design of the reflector and hence a thin design of the vehicular lamp.
FIG. 9 shows one example of the conventional structure of the reflector. Aluminum or the like is vapor deposited on an inner surface of a lamp body 1A to form a reflector 6, and a bulb 5 is attached to the lamp body through a bulb socket 4 mounted in a bulb mounting hole 3 formed in a rear surface of the lamp body 1A. A lens 2 is mounted at a front opening in the lamp body 1A. A reflective surface of the reflector 6 is divided into a plurality of regions in a right-left direction, and each of these division regions defines a band-like divided surface 61 extending in an upward-downward direction, and these divided surfaces are offset a predetermined amount or different amounts rearwardly in the direction of the optical axis, and the divided surfaces 61 are interconnected to form one continuous reflective surface. Therefore, in this lamp body 1A, the overall dimension in the direction of the optical axis is reduced while the parabolic shape of each divided surface 61 is maintained, and light from the bulb 5 is reflected by the parabolic reflector, and the thin design of the reflector can be achieved.
In the conventional reflector, however, a relatively-sharp step portion 67 is inevitably formed at an interconnecting (continuous) portion where each two adjacent divided surfaces 61 are continuous with each other. FIG. 10A is a view showing the step portions 67 on an enlarged scale, and a surface (hereinafter referred to as "continuous surface") 62 of the continuous portion, formed between each two adjacent divided surfaces 61, is directed away from the direction of the light emitted from the bulb 5, and the step portions 67, forming a serrated cross-section, are formed by the continuous surfaces 62. Therefore, the light, emitting from the bulb 5, is intercepted by the step portions 67, and the bulb light is not applied to each continuous surface 62 and part of the divided surface 61 disposed outwardly adjacent thereto, and the amount of the reflected light is reduced or becomes almost zero at these portions, and when the vehicular lamp is seen from the front side thereof during the lighting, these continuous portions form stripe-like, dim illuminating portions, as shown in FIG. 10B.
On the other hand, the knife edge-like end of each step portion 67 intensely reflects the bulb light in one direction, and these portions form stripe-like illuminating portions brighter than the other portions. Therefore, the light distribution characteristics are such that the bright and dim illuminating portions are arranged in a striped manner, and the light distribution characteristics, providing a uniform light intensity, can not be obtained, and besides this detracts from the appearance.
In this kind of vehicular lamp, in some cases, one side portion thereof is curved along a side surface of a vehicle body to form a so-called round corner portion. If this round corner portion is formed when the reflector is constituted by the divided surfaces as described above, the bulb light-intercepting phenomenon, caused by the above-mentioned step portions, becomes more conspicuous, so that there is a possibility that the appearance of the vehicular lamp is further degraded by the stripe-like bright and dim illuminating portions at the round corner portion.